1. Field of the Invention
The present invention relates to a variable magnification lens and an imaging apparatus using this variable magnification lens.
2. Description of Related Art
A conventional variable magnification lens has a two-lens-unit arrangement that includes, in order from the object side, a front lens unit with positive power and a rear lens unit with negative power. Such variable magnification lenses, which are simple in lens barrel structure, are often used with respect to low-cost lenses in the main. Many variable magnification lenses in which aspherical lens components are used to reduce the number of lens components are proposed.
In the two-lens-unit arrangements, even the variable magnification lenses with a variable magnification ratio of approximately 2 are often constructed so that a plurality of aspherical lens components are used in the front lens unit, lens components are cemented to each other, or a plurality of lens components are used in the rear lens unit to correct aberration.
In the conventional variable magnification lenses of the two-lens-unit arrangements, both the front and rear lens units sometimes have aspherical lens components. In many of the low-cost optical systems, aspherical lens components are constructed of plastic and are susceptible to the influences of changes of circumstances, such as temperature and humidity. On the other hand, aspherical lens components constructed of glass are little affected by the changes of circumstances.